remove MSG.cs, merge content from MSG.cs and ChatMessage.cs, refactor code

PolyChat/Models/MSG.cs

@@ -1,29 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Net;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace PolyChat.Models
-{
-    /// <summary>
-    /// dumy class for json converter
-    /// </summary>
-    public class MSG 
-    {
-        public string sender = "unknown";
-        public DateTime timestamp = new DateTime(2000, 01, 01);
-        public string msg = "empty";
-        public string ip;
-
-
-        public MSG(string sender, string ip, String msg, DateTime timestamp)
-        {
-            this.sender = sender;
-            this.ip = ip;
-            this.timestamp = timestamp;
-            this.msg = msg;
-        }
-    }
-}